Impact of Manipulation Under Anesthesia on Functional Outcomes Following Total Knee Arthroplasty: A Systematic Review of the Knee Society Score (KSS), Oxford Knee Score (OKS), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)

Postoperative stiffness remains a significant complication following total knee arthroplasty (TKA), affecting functional recovery and patient satisfaction. Manipulation under anesthesia (MUA) is commonly employed when conservative measures fail, yet the impact on patient-reported outcomes remains unclear. This systematic review evaluated functional outcomes following MUA, focusing on the Knee Society Score (KSS), Oxford Knee Score (OKS), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores. A comprehensive search of PubMed, Embase, Scopus, and the Cochrane Library was conducted up to February 1, 2026, in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. Six studies, including retrospective and prospective cohorts and a systematic review, were included. Early MUA (<8-12 weeks) consistently achieved a superior range of motion (ROM) gains (+25° to +34°) compared to delayed interventions. Functional outcomes showed modest short-term improvements with sustained long-term benefits, and complications were rare. While ROM gains were reliably achieved, patient-perceived functional recovery depended on pain control, rehabilitation adherence, and individual factors. Early and standardized MUA is effective for improving mobility and functional recovery after TKA. Future high-quality prospective studies are warranted to refine timing, standardize techniques, and clarify the relationship between mechanical improvements and patient-centered outcomes.